There is tons of stuff to do in Dubrovnik. The city is a true reflection of its history and has a great beauty. It's surrounded by a wall that houses 16 towers from which you can see the whole city. The main entrance is near the Church of St. Spasa, from which you can take part in one of the many popular Dubrovnik activities: an hour and a half walking tour to admire the scenery. Its cathedral, Velike Gospe, is one of the major places to visit in Dubrovnik.
The Pile Gate, another one of the many things to do in Dubrovnik, is an open semicircular bastion, and from it you can access the large stone path, Plate, leading to a more aristocratic area with baroque palaces.
Nearby is Luza Square, extending south to the magnificent Rector's Palace, which has been converted into the city's Museum of the History. This palace is another one of the important monuments and Dubrovnik attractions. It was the seat of government and the rector when Dubrovnik was an independent republic.
Since it's a coastal city, we can't forget the worthwhile beaches as yet more things to see in Dubrovnik. The most important is perhaps Gradska beach, but you can easily access others using public transport or a private car. You can also visit the island of Lokrum, one of the most unique and beautiful attractions in Dubrovnik. Hopefully you enjoy exploring the city thoroughly and learning all there is to know about what to do in Dubrovnik, like strolling in the fresh air. It really is a different place.